Vinyl halide polymers, both rigid and flexible vinyl chloride polymers, are being used increasingly in the construction industry, as well as in fabrics, wall coverings and upholstery materials. As a result of recent hotel and high rise apartment building fires, there is a need that these materials be modified to reduce the amount of smoke evolved and to improve their fire retarding characteristics in the event of a fire.
Accordingly, many additives and combinations of additives have been added and proposed by the prior art in an attempt to improve the fire and smoke retardant characteristics of vinyl halide polymers.
In U.S. Pat. No. 3,644,589, Moore et al disclose that the self-extinguishing properties of impact-modified polyvinyl chloride can be improved by inclusion in the compositions of selected tin compounds, namely, organotin maleates, organotin mercaptides, stannous oxide and mixtures thereof. Later, Kroenke in U.S. Pat. No. 4,055,537 disclosed that polyvinyl chloride can be rendered smoke retardant by incorporating therein a synergistic mixture of melamine molybdate with a host of metal oxides including stannic oxide.
Several prior art workers have suggested specific metal oxalates as additives which can be combined with other compounds to provide smoke retardant polyvinyl chloride. Thus, Dickens in U.S. Pat. No. 3,965,068 disclosed fire retarding polyvinyl chloride with a synergistic mixture of selected nickel compound and selected zinc compounds including zinc oxalate.
In U.S. Pat. No. 3,968,081, Dickens disclosed that polyvinyl chloride can be smoke retarded by the inclusion of a synergistic mixture of vanadium pentoxide and selected nickel compounds including nickel oxalate. Kroenke in U.S. Pat. No. 4,053,454 disclosed that PVC can be rendered smoke retardant by the incorporation therein of a synergistic mixture of a melamine molybdate and selected nickel compounds including nickel (II) oxalate.
McRowe et al in U.S. Pat. Nos. 4,054,453 and 4,507,414 disclosed that smoke generation can be suppressed in polyvinyl chloride by the incorporation therein of copper oxalate and amine molybdates, such as melamine molybdates. Later, Brown in U.S. Pat. No. 4,464,495 disclosed that polyvinyl chlorides that had been rendered smoke retardant by the inclusion of copper oxalate and amine molybdates can be further improved by the addition of alkaline earth metal carbonates, titanium dioxide and aluminum trihydrate.
Dorfman et al in U.S. Pat. No. 4,013,815 suggest the use of ferric oxalate in halogenated polyesters, but not in polyvinyl chloride.
The oxalates of nickel, copper and zinc are too expensive to include in polyvinyl chloride compositions. They also suffer the disadvantage of requiring expensive or exotic additives in synergistic combinations. Moreover, copper oxalate is blue-white, and nickel oxalate is light green, and hence may adversely color the products containing them.
Accordingly, it is an object of this invention to provide polyvinyl halide compositions having improved smoke retarding characteristics by the inclusion of inexpensive additives which do not require the use of expensive or exotic synergistic compounds. It is a further object of the invention to provide flame retardant polyvinyl halide compositions, for applications, both rigid and flexible, which have improved smoke retarding properties.
A further object of the invention is to provide in a cost effective manner, colorless to white, transparent or translucent polyvinyl chloride compositions having improved flame retarding properties and reduced smoke generating characteristics.
Further objects of the invention will become apparent upon consideration of the following specification.